Aqueous Coating Systems Based On Physically Drying Urethane Acrylates

Abstract

The invention relates to radiation-curable coating systems based on aqueous polyurethane dispersions, to a process for their production, to the use of the coating systems as lacquers and/or adhesives, and also to articles and substrates provided with these lacquers and/or adhesive.

1 . A radiation-curable, aqueous dispersion based on polyurethane acrylates (i) comprising as structural components
 A) an oligomeric or polymeric compound comprising an isocyanate-reactive group and a radically copolymerisable group;   B) optionally a monomeric compound other than A comprising a hydroxy functional group and a (meth)acrylate group;   C) a polyester polyol obtained from
 C1) an aliphatic diol comprising from 2 to 4 carbon atoms between the two OH functional groups of said aliphatic diol and/or an aliphatic triol, and 
 C2) an aromatic di- and/or tri-carboxylic acid; 
   D) optionally a polyol other than A, B, and C;   E) a compound comprising an isocyanate-reactive group towards and a non-ionic group, an ionic group, or a group capable of forming an ionic group, wherein said compound has a dispersing action;   F) an organic polyisocyanate;   G) optionally a compound other than A, B, C, D, and E comprising an isocyanate-reactive group.   
   
   
       2 . The radiation-curable, aqueous dispersion of  claim 1 , further comprising a reactive diluent (ii) comprising a radically polymerisable group. 
   
   
       3 . The radiation-curable, aqueous dispersion of  claim 1 , wherein structural component C is used in an amount of from 5 to 75 weight %, wherein the sum of the amounts of components A, B, C, D, E, F, and G equals 100 weight %. 
   
   
       4 . The radiation-curable, aqueous dispersion of  claim 1 , wherein structural component C has an OH number in the range of from 20 to 500 mg KOH/g of substance. 
   
   
       5 . The radiation-curable, aqueous dispersion of  claim 1 , wherein structural component A is selected from the group consisting of polyester(meth)acrylates comprising hydroxyl groups, polyether(meth)acrylates comprising hydroxyl groups, polyether ester(meth)acrylates comprising hydroxyl groups, and polyepoxy(meth)acrylates comprising hydroxyl groups. 
   
   
       6 . The radiation-curable, aqueous dispersion of  claim 1 , wherein component C1 is selected from the group consisting of 1,2-ethanediol, 1,2-propanediol, 1,3-propanediol, neopentyl glycol, 2-ethyl-2-butylpropanediol, 1,3-butanediol, 1,2-cyclohexanediol, 1,4-cyclohexanediol, 1,4-butanediol, trimethylolethane, trimethylolpropane, trimethylolbutane, glycerol, castor oil, and mixtures thereof and component C2 is selected from the group consisting of phthalic acid, phthalic anhydride, isophthalic acid, isophthalic anhydride, terephthalic acid, terephthalic anhydride, trimellitic acid, trimellitic anhydride, and mixtures thereof. 
   
   
       7 . The radiation-curable, aqueous dispersion of  claim 1 , wherein component C1 is selected from the group consisting of 1,2-ethanediol, 1,2-propanediol, neopentyl glycol, trimethylolpropane, and mixtures thereof, and component C2 is selected from the group consisting of isophthalic acid, terephthalic acid, and mixtures thereof. 
   
   
       8 . The radiation-curable, aqueous dispersion of  claim 1 , wherein structural component E is selected from the group consisting of 2-(2-amino-ethylamino)ethanesulfonic acid, 3-(cyclohexylamino)propane-1-sulfonic acid, the addition product of isophoronediamine and acrylic acid, hydroxypivalic acid, dimethylolpropionic acid, triethanolamine, tripropanolamine, N-methyldiethanolamine, N,N-dimethylethanolamine, monofunctional mixed polyalkylene oxide polyethers containing at least 40 mol % ethylene oxide units and no more than 60 mol % propylene oxide units, and mixtures thereof. 
   
   
       9 . The radiation-curable, aqueous dispersion of  claim 1 , wherein structural component F is selected from the group consisting of the polyisocyanates 1,6-hexamethylene diisocyanate, 1-isocyanato-3,3,5-trimethyl-5-isocyanatomethylcyclohexane, 4,4′-diisocyanato-dicyclohexylmethane, and mixtures thereof; homologues of 1-isocyanato-3,3,5-trimethyl-5-isocyanatomethylcyclohexane with biuret, carbodiimide, isocyanurate, allophanate, iminooxadiazinedione, and/or uretdione groups, oligomers of 1-isocyanato-3,3,5-trimethyl-5-isocyanatomethylcyclohexane with biuret, carbodiimide, isocyanurate, allophanate, iminooxadiazinedione, and/or uretdione groups, homologues of 4,4′-diisocyanato-dicyclohexylmethane with biuret, carbodiimide, isocyanurate, allophanate, iminooxadiazinedione, and/or uretdione groups, oligomers of 4,4′-diisocyanato-dicyclohexylmethane with biuret, carbodiimide, isocyanurate, allophanate, iminooxadiazinedione, and/or uretdione groups, and mixtures thereof; and mixtures of said homologues and/or said oligomers with said polyisocyanates. 
   
   
       10 . A process for preparing the radiation-curable, aqueous dispersion of  claim 1 , comprising
 reacting components A, B, C, D, and E in one or more reaction steps with component F to obtain a polyurethane acrylate prepolymer (i), wherein a neutralising agent for producing ionic groups is optionally added before, during, or after the preparation of said polyurethane acrylate prepolymer;   adding water to said polyurethane acrylate prepolymer or converting said polyurethane acrylate prepolymer into an aqueous initial charge to obtain a dispersion; and   optionally chain extending said polyurethane acrylate prepolymer with component G before, during or after obtaining said dispersion.   
   
   
       11 . The process of  claim 10 , wherein the molar ratios of isocyanate groups in F to isocyanate-reactive groups in A, B, C, D and E is from 0.8:1 to 2.5:1. 
   
   
       12 . The process of  claim 10 , wherein one more reactive diluents having at least one radically polymerisable group (component ii) is/are added as a further component. 
   
   
       13 . A coating, lacquer, or adhesive comprising the radiation-curable, aqueous dispersion of  claim 1 . 
   
   
       14 . A coating composition comprising the radiation-curable, aqueous dispersion of  claim 1 , a crosslinker based on an amino resin, a blocked polyisocyanate, a non-blocked polyisocyanate, a polyaziridine and/or a polycarbodiimide, and/or a further dispersion. 
   
   
       15 . A substrate coated with coating composition of  claim 14 .